Article 298: The Fundamental Fault in the Legal Case to Cede Chagos
The debate over the proposed signing of the UK-Mauritius Agreement concerning the Chagos Archipelago has triggered debate over the scope of international maritime law. In defending the decision to cede British Indian Ocean Territory (BIOT), the UK Government hinged its argument on an "imminent legal threat” that could be raised by Mauritius under the United Nations Convention on the Law of the Sea (UNCLOS).
RESEARCHBRITISH INDIAN OCEAN TERRITORY
The debate over the proposed signing of the UK-Mauritius Agreement concerning the Chagos Archipelago has triggered debate over the scope of international maritime law. In defending the decision to cede British Indian Ocean Territory (BIOT), the UK Government hinged its argument on an "imminent legal threat” that could be raised by Mauritius under the United Nations Convention on the Law of the Sea (UNCLOS).
This concern was echoed on 22 May 2025, when Defence Secretary John Healey told Parliament that without the deal the UK could face losing legal rulings, and within just a few years the military base of Diego Garcia would become inoperable.
However, the key question is whether UNCLOS tribunals could in fact exercise compulsory jurisdiction over disputes concerning the Chagos Archipelago. And, if so, how far would that jurisdiction extend?
While UNCLOS establishes broad jurisdiction over maritime activities, it has no legal power to rule on territorial disputes as it is restricted to disputes arising around ocean governance.
Furthermore, the treaty provides a specific mechanism for states to opt out of compulsory dispute resolution; UNCLOS Article 298(1)(b) excludes “disputes concerning military activities”, an exclusion that applies to the entirety of BIOT rather than being solely restricted to the individual island of Diego Garcia.
The United Kingdom formally lodged its declaration under Article 298 in 2003, and it was reaffirmed in 2020. The UK’s declaration under Article 298(1)(b), excluding disputes concerning military activities from UNCLOS compulsory dispute settlement procedures, provides an additional jurisdictional safeguard against compulsory UNCLOS proceedings that concern military operations in the Chagos Archipelago.
In practical terms, this limits the ability of UNCLOS tribunals to exercise jurisdiction over disputes directly related to military and defence activities. Consequently, international tribunals and courts under UNCLOS cannot exercise compulsory jurisdiction over disputes concerning military activities, such as in Chagos.
The UK has administered the maritime zones throughout the BIOT in accordance with UNCLOS, as evidenced by the official geographical coordinates deposited by the UK with the United Nations Secretariat. Specifically, in September 1991, 200-nautical-mile “Fisheries Conservation and Management Zone", followed by a 2003 establishment of “Environment Protection and Preservation Zone” under the explicit legal framework of UNCLOS.
These measures demonstrate that the UK has applied UNCLOS as the governing framework for maritime administration across the Chagos Archipelago and not solely around the military base. Thus, Article 298 cannot reasonably be understood as applying exclusively to Diego Garcia. The UK's maritime zones and wider administration of BIOT under the UNCLOS framework indicate that the declaration operates across the territory's maritime domain as a whole.
The existence of the Article 298 military-activities exception raises questions about the extent of legal risk identified by John Healey. If the UK is actually managing the British Indian Ocean Territory as a single entity, it could be argued that the whole territory may fall within this exception.
Rather than rushing toward a transfer of sovereignty, the UK could pursue an alternative solution centred on the rights and wishes of the Chagossian people. The time constraint is not about avoiding an “imminent legal threat,” but about ensuring that those with ancestral ties to the British Indian Ocean Territory are finally given a decisive voice in determining the constitutional future of the Archipelago. The UK can build up a self-determination mechanism focusing on the rights of the Chagossians.
Since February 2026, there has been a British Chagossian presence on the outer island, Ile du Coin, in Peros Banhos atoll. This presence reflects the community’s fight for resettlement and self‐determination. The UK can temporarily administer the whole BIOT while self-determination arrangements are established. Under that approach, continued UK administration would be justified not as a permanent settlement of sovereignty. It would be a temporary arrangement until a democratic determination of the wishes of the population is agreed. The Chagossian people deserve a genuine opportunity to determine their political future.
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